The current trend of mobility drives the consumer demand towards ever smaller portable devices, such as mobile phones, portable digital assistants, music and video players, laptop PCs, head mounted displays etc. As the size becomes smaller and the functionality higher, there is a fundamental problem of showing large enough visual images with very small devices. Because the size of a fixed screen cannot grow without increasing the size of the device itself, the only reasonable way to conveniently provide visual images from small devices is to project them using a data projector. However, the current data projectors are large in size and inefficient in nature.
The commercially available data projectors use high intensity broadband light sources, such as incandescent bulbs or arc lamps. These light sources have inherently low efficiency and produce heat, which consumes high amounts of energy and requires a cooling system. The use of LED as a light source of data projector has also been proposed. However, these solutions do not have well enough optical efficiency. In these systems, the light source has poor external efficiency, and in addition to that, a large part of the light is lost in collimation. Secondly, these solutions are still large in size and expensive with high power consumption, and they cannot be operated with widely used battery technologies.
Another issue that is of interest to large audiences in image projection is the issue of 3-dimensional (3D) projection. The current data projectors are not inherently capable of showing full color 3D images and the special devices that are designed to do so are expensive and rare. The media industry increases the offering on 3D movies, games and other entertainment only if 3D capable devices are commonly used.